EP3211452B1 - Device for detecting objects carried by an individual - Google Patents

Description

• De détecteurs de métaux, qui ne peuvent bien sûr pas détecter les objets non métalliques tels que les explosifs ;
• De dispositifs à rayons X, utilisables pour des bagages par exemple, mais pas en zone ouverte pour des raisons de santé publique ;
• D'autorisations de fouilles, mais celles-ci sont lentes et peuvent être contestées.

The present invention relates to a device for detecting objects carried by an individual, immobile or moving, these objects may be illicit objects hidden under clothing.
The surveillance of people in public places has become a necessity of public security. There is a growing need to control what people carry. In the street, there is a real need to detect explosives, weapons or drugs. In trains, you have to detect explosives or weapons. In stadiums, in addition to these dangerous objects, it is useful to detect bottles of glasses or drugs in particular.
Current control solutions are insufficient. Security forces have:

• Metal detectors, which of course can not detect non-metallic objects such as explosives;
• X-ray devices, usable for luggage for example, but not in an open area for reasons of public health;
• Excavation permits, but these are slow and can be challenged.

• au moins une antenne rotative comportant au moins deux guides d'onde rectilignes parallèles et un cylindre pourvu d'une fente hélicoïdale mobile en rotation autour desdits guides, lesquels sont ouverts en regard de la face intérieure dudit cylindre mobile, ladite surface formant un court-circuit hyperfréquence pour fermer lesdits guides, un desdits guides étant dédié à l'émission, une source rayonnante mobile étant en regard desdits guides par suite du mouvement de rotation dudit cylindre induisant un faisceau d'émission et de réception mobile apte à être orienté vers un individu ;
• un radar émettant un signal hyperfréquence selon une onde continue (CW) vers le guide d'émission de ladite antenne et recevant les signaux reçus des guides de ladite antenne captés par ledit faisceau mobile, lesdits signaux reçus étant la composante directe I et la composante en quadrature ;
• une caméra stéréoscopique orientée dans la même direction que ledit faisceau mobile, apte à enregistrer l'enveloppe vestimentaire dudit individu, ladite enveloppe servant de surface de référence pour la mesure des distances audit dispositif ;
• un calculateur calculant une image de type SAR de la partie du corps dudit individu ciblée par ledit radar et ladite caméra équipé d'éventuels objets, à partir des signaux reçus dudit radar et des distances mesurées par ladite caméra.

The documents FR 3 003 959 A1 and FR 2 844 642 A1 disclose a radar system equipped with a rotating helical slot antenna for radar imaging to detect dangerous objects worn by an individual. The document WO 2015/059132 A2 discloses a synthetic aperture radar combined with a stereoscopic camera for detecting dangerous objects carried by an individual. An object of the invention is to overcome these disadvantages and to allow the detection of illicit objects carried by individuals, moving or immobile, simply and quickly.
To this end, the invention relates to a device for detecting objects carried by individuals, immobile or in motion, said device comprising at least:

• at least one rotary antenna comprising at least two parallel rectilinear waveguides and a cylinder provided with a helical slot rotatable around said guides, which are open opposite the inner face of said movable cylinder, said surface forming a short microwave circuit for closing said guides, one of said guides being dedicated to the emission, a moving radiating source being opposite to said guides as a result of the rotational movement of said cylinder inducing a mobile transmitting and receiving beam adapted to be directed towards an individual;
• a radar emitting a microwave signal in a continuous wave (CW) towards the transmission guide of said antenna and receiving the signals received from the guides of said antenna picked up by said moving beam, said received signals being the direct component I and the component in quadrature;
• a stereoscopic camera oriented in the same direction as said moving beam, able to record the clothing envelope of said individual, said envelope serving as a reference surface for measuring the distances to said device;
• a calculator calculating a SAR-type image of the part of the body of said individual targeted by said radar and said camera equipped with any objects, from the signals received from said radar and the distances measured by said camera.

In a particular embodiment, the two guides are engraved in a cylinder disposed inside the mobile cylinder, the two cylinders having the same axis, and the space between the two cylinders is equal to 0.1 mm ± 0.05 mm.

Said rotary antenna comprises, for example, a system for minimizing microwave leakage, said system being composed of three cavities, said cavities being arranged in pairs on each side of said waveguides, parallel to these, along their entire length.

Said waveguides being engraved in a cylinder disposed inside the mobile cylinder, said mobile cylinder and said inner cylinder are for example rotatable by means of a ball bearing device, the base of said movable cylinder. and the base of said inner cylinder being respectively mechanically secured to the movable part and the fixed part of said device.

Said radar operates for example in a millimetric frequency band.

In one possible embodiment, said device comprises two rotary antennas for said radar to operate in bi-static mode, one antenna transmitting and the other antenna being dedicated to reception.

In this possible embodiment, the antennas are for example interconnected by two waveguides, a guide connecting the transmission guides of said antennas and the other guide connecting the reception guides, the first waveguide being connected via a magic T to a waveguide connected to the radar and the second waveguide being connected via another magic T to a waveguide connected to the radar.
Said radar emits, for example, according to a number N of frequencies close to a given frequency, the emission pulse being divided into N parts, each part corresponding to a frequency, a first level of analysis of the image being carried out for the signals received at the first of said frequencies, other analyzes being carried out for the signals received at the other frequencies, the various analyzes making it possible to approach the theoretical value of the dielectric permittivity of a detected object.
The computer is for example an integral part of the processing means of said radar.
Said device comprising means for displaying the images obtained, said viewing means are for example glasses worn by a user and on which said images are projected.
The antenna part, the radar and their interconnection means are arranged inside a portable cylindrical structure, also acting as a radome, said structure supporting said camera.

• La figure 1, les principaux composants formant un dispositif selon l'invention ;
• Les figures 2a et 2b, le principe de réalisation de l'antenne rotative utilisée dans le dispositif selon l'invention ;
• La figure 3, une vue transversale de ladite antenne ;
• Les figures 4a à 4e, une illustration du fonctionnement de ladite antenne ;
• Les figures 5a et 5b, un exemple de réalisation de ladite antenne ;
• Les figures 6a et 6b, un exemple de réalisation permettant de minimiser les fuites hyperfréquence au niveau de ladite antenne ;
• La figure 7, une vue en coupe longitudinale de ladite antenne ;
• Les figures 8a et 8b, un exemple de réalisation d'un dispositif selon l'invention permettant un fonctionnement de type bi-statique ;
• La figure 9, une illustration du fonctionnement mono-statique et une illustration du fonctionnement bi-statique ;
• La figure 10, une illustration de la détection d'un objet à travers un vêtement ;
• La figure 11, une zone détection soumise à l'analyse d'un signal multifréquences ;
• La figure 12, un exemple de réalisation d'un dispositif selon l'invention, portable ;
• La figure 13, un exemple d'application de dispositifs selon l'invention équipant des portes pour le contrôle d'un passage.

Other characteristics and advantages of the invention will become apparent with the aid of the description which follows, given with regard to appended drawings which represent:

• The figure 1 the main components forming a device according to the invention;
• The Figures 2a and 2b , the principle of realization of the rotary antenna used in the device according to the invention;
• The figure 3 a transverse view of said antenna;
• The Figures 4a to 4e an illustration of the operation of said antenna;
• The figures 5a and 5b an embodiment of said antenna;
• The Figures 6a and 6b an exemplary embodiment for minimizing microwave leakage at said antenna;
• The figure 7 a longitudinal sectional view of said antenna;
• The Figures 8a and 8b , an exemplary embodiment of a device according to the invention for a bi-static type operation;
• The figure 9 , an illustration of the mono-static operation and an illustration of the bi-static operation;
• The figure 10 , an illustration of the detection of an object through a garment;
• The figure 11 a detection zone subjected to the analysis of a multifrequency signal;
• The figure 12 , an exemplary embodiment of a device according to the invention, portable;
• The figure 13 , an example of application of devices according to the invention equipping doors for the control of a passage.

• une antenne rotative 1 dont le fonctionnement sera décrit par la suite et que l'on pourra appeler également scanner ;
• un radar 2, à onde continue (CW) fonctionnant par exemple à une fréquence centrale proche de 77 GHz, à faible coût fonctionnant en mode de réception homodyne, et comportant notamment la génération des ondes d'émission à la fréquence centrale, les moyens de réception et les moyens d'émission, le radar 2 fournissant une image radar à partir des signaux reçus par l'antenne rotative selon le principe de l'imagerie SAR comme cela sera décrit par la suite ;
• deux guides d'onde 3, 4 assurant pour l'un la transmission des signaux hyperfréquences du radar 2 vers l'antenne 1 et pour l'autre de l'antenne vers le radar ;
• une caméra stéréoscopique 5, par exemple de type Kinect ;
• un calculateur 6 combinant l'image obtenue par la caméra avec l'image obtenue par le radar afin de visualiser les éventuels objets détectés en superposition de l'image stéréoscopique obtenue par la caméra ;
• un écran 7 ou tout autre moyen de visualisation, reliée au calculateur, affichant l'image finale.

The figure 1 illustrates the main components forming a device according to the invention. It includes at least:

• a rotary antenna 1 whose operation will be described later and that we can also call scanner;
• a continuous-wave (CW) radar 2 operating, for example, at a central frequency close to 77 GHz, at low cost operating in homodyne reception mode, and comprising in particular the generation of transmission waves at the central frequency, the means of reception and transmission means, the radar 2 providing a radar image from the signals received by the rotating antenna according to the principle of SAR imaging as will be described later;
• two waveguides 3, 4 ensuring for one the transmission of the microwave signals from the radar 2 to the antenna 1 and the other from the antenna to the radar;
• a stereoscopic camera 5, for example of the Kinect type;
• a calculator 6 combining the image obtained by the camera with the image obtained by the radar in order to visualize any detected objects superimposed on the stereoscopic image obtained by the camera;
• a screen 7 or any other visualization means, connected to the computer, displaying the final image.

The various components of the device according to the invention will be described later.

The Figures 2a and 2b illustrate the principle of possible realization of the scanner 1. The figure 2 illustrates the principle of realization. The antenna 1 comprises a metal cylinder 21 having a radiating opening 22 in a helical line 23 running around the cylinder. The antenna comprises at least one pair of waveguides 24, 25 disposed inside the cylinder and open towards the inner wall of the cylinder. A waveguide 24 is reserved for transmission and the other waveguide 25 is reserved for reception. The transmission guide 24 is connected to the transmitting means of the radar 2 and the reception guide 25 is connected to the reception means of the radar 2. The cylinder 21 and the waveguides 24, 25 have a relative rotational movement relative to the axis 100 of the cylinder.
Preferably, the guides remain fixed and the cylinder 21 is rotated around the guides. The guides 24, 25 are placed on a support 26 disposed inside the cylinder 21.

The figure 2b illustrates an exemplary embodiment of the support 26 of the waveguides 24, 25. This support 26, disposed inside the first cylinder 21, is a cylinder. It forms the stator in the case where the first cylinder 21, the rotor, is driven by a rotational movement. The waveguides 24, 25 are arranged on the inner cylinder 26. In a preferred embodiment, the guides 24, 25 are etched in this cylinder 26. In fact, given the speed of movement of the people to be monitored , from 0.5 to 3 km / h, to obtain a good sampling of the synthetic antenna, at 0.5 λ (λ being the length of the microwave wave used), the speed of rotation of the rotor must be understood between 1500 and 3000 revolutions per minute, which excludes any asymmetry of the stator. This imposes a stator with a cylindrical outer envelope, and thus waveguides etched in the cylinder.
The antenna 1 comprises two guides 24, 25, one in transmission and the other in reception, these two distinct guides advantageously allowing a car real-time calibration. Indeed, any mechanical system operating at rotation speeds such as that previously announced requires a calibration system almost in real time. This calibration requires the measurement of the different microwave paths inside the device which can be advantageously achieved by the external coupling between the emission produced by the transmission guide 24 and the reception on the other guide 25, thus enabling actions preventative measures against disturbances.

The figure 3 presents by a transverse view the arrangement of the inner cylinder 26 with respect to the outer cylinder 21, the two cylinders having the same axis of symmetry 100. The diameter of the inner cylinder 26 is for example defined so that the radiating face of the guides is at a given distance from the outer cylinder that will be specified later. When the radiating face is facing the inner metallized portion of the cylinder, and not the opening, this metallized face acts as a short microwave circuit, without preventing leaks at the contacts. In order to avoid these large leaks, along the emission and reception waveguides 24, three slots are provided, engraved in the inner cylinder acting as short circuits making it possible to reduce short circuits to the level of the guides. An example of realization of these slots will be presented to Figures 6a and 6b .
The principle of realization of the rotary antenna illustrated by the Figures 2a, 2b and 3 uses a pair of waveguides 24, 25, one for transmission and the other for reception. It is possible to provide an embodiment comprising two pairs of waveguides (transmission and reception). In this case, the second pair is for example diametrically opposed to the first pair 24, 25. The two pairs of guides are then for example connected to the radar 2 via an SP4T switch. Advantageously, such an antenna makes it possible to increase the control domain.

• dans la direction perpendiculaire au mouvement du porteur par la résolution en distance du radar ;
• dans la direction du mouvement du porteur par la largeur du faisceau F1.

Le traitement du type SAR est notamment décrit dans l'ouvrage de J.Darricau : Physique et Théorie du Radar -Tome 3, 3ème édition - Chapitre 21, page 483 - Editeur Sodipe, Paris 1994 .
Un ensemble de récepteurs disposés le long de l'axe 43 est alors reconstitué dans le temps comme dans une application de type SAR, permettant ainsi de réaliser des images radar. En effet, à partir des coefficients de réflexion mesurés pour chaque pixel de l'image on reconstitue la forme des objets.The Figures 4a, 4b , 4c, 4d and 4th illustrate the operation of an antenna as described above, more particularly the detection mode that it allows. The Figures 4a and 4b represent a partial sectional view, along the axis 100, of two relative positions of the cylinders 21, 26. Figures 4c and 4d respectively illustrate the relative positions of the two cylinders partial views of Figures 4a and 4b by views from above. These figures show that in the presence of the outer cylinder 26, the slots 24, 25 form two non-contact microwave waveguides, the rotation of the inner cylinder 26 opposite the fixed outer cylinder and open longitudinally forming two mobile radiating sources.
To facilitate the explanation of this phenomenon, consider a single beam, corresponding for example to the emission waveguide 24. In operation, the portions of the guide 24 which face the metallized wall of the cylinder 21 do not radiate. The portions of the guide which are opposite the opening 22 participate in the radiation of the antenna, transmission and reception. In fact, because of the helical shape of the waveguide 25 in a helix and its rotation relative to the longitudinal opening 22 of the fixed cylinder, the guide 24 is presented opposite the opening as a sliding guide element. making straight round trips.
The figure 4a illustrates the position of a portion of the guide 24 with respect to the opening radiating at a given instant t ₀ . The figure 4e illustrates the antenna beam F ₁ associated with the position of the figure 4a with its phase center 41 located at the guide portion 24 forming an illuminator or radiating source. The beam F ₁ here represents the angular coverage of the antenna. The figure 4b illustrates the same elements as those of the figure 4a , but at a time following t ₀ + Δt. In the plane of the figure, the portion of the guide 24 radiating source, opposite the opening 22, then shifted by a distance Δ due to the rotation of the inner cylinder 26. The antenna beam F ₁ corresponding to the inner cylinder position 26 of
the figure 4b is represented with its phase center 42 which has shifted by a distance Δ. The rotation of the inner cylinder supporting the guide 24 thus allows the continuous displacement of the phase center of the radiation and thus of the beam F ₁ . Along the axis 43 of the longitudinal opening 22, parallel to the axis 100 of the cylinder, the phase center moves between a position x ₀ - Δ _Max / 2 and x ₀ + Δ _Max / 2. The amplitude of displacement Δ _Max depends on the pitch of the helix 23 that follows the radiating opening. The rotational speed of the inner cylinder 26 is such that the phase center 41, 42 moves linearly at a speed of up to 30 m / s.
The width of the beam F ₁ is a function of the width d of the opening 22 of the outer cylinder, forming a radiating opening. More is small, the more Antenna beam is wide. The width at 3dB of the beam F ₁ is λ / d, where λ is the wavelength emitted. The scanning principle is the same in reception with the reception guide 25.
The rotation of the inner cylinder thus allows the continuous displacement of the phase center of the radiation, and thus makes it possible to obtain a synthetic antenna or SAR type radar operation. This property is by the radar processing means 2 to obtain and analyze high resolution radar images. For the record, synthetic antenna radars are radars whose antenna is oriented perpendicular to the carrier's road. It is the carrier of the radar, and more particularly of the antenna, which in its displacement generates the observation of the space. In this case, the movement of the carrier is simulated by the displacement of the phase center. The two dimensions of the radar image are defined by the direction of propagation and the movement of the carrier. The spatial resolution, which conditions the fineness of the image observed, is thus obtained:

• in the direction perpendicular to the movement of the carrier by the distance resolution of the radar;
• in the direction of the movement of the carrier by the width of the beam F1.

The SAR type processing is described in particular in J.Darricau: Physics and Radar Theory -Tome 3, 3rd edition - Chapter 21, page 483 - Publisher Sodipe, Paris 1994 .
A set of receivers arranged along the axis 43 is then reconstituted in time as in a SAR-type application, thus making it possible to produce radar images. Indeed, from the reflection coefficients measured for each pixel of the image is reconstructed the shape of the objects.

In the embodiment described by the Figures 2a and 2b , the inner cylinder 26 comprising the two waveguides 24, 25 is fixed, the two guides being rectilinear. The rotor 21 has the helical slot 22 which rotates around the guides.
It is possible to provide an embodiment where the inner cylinder 26 equipped with rotating waveguides, forming a rotor, while the helical slot 22 remains fixed.

In another embodiment, the waveguides have a helical shape and the slot in rotation around the guides is rectilinear. This rotational movement is relative, that is to say either the slots can be fixed and the slot rotatable, or conversely the guides are rotatable and the slot is fixed.
When the hollow cylinder carrying the slot is fixed, it can act as a radome, also avoiding that the slot deforms under the effect of rotation. Rotating waveguides, however, require a rotating joint system and a mechanism adapted to exchange the signals with the radar. For all these embodiments, the operating principle remains that described in Figures 4a to 4e . Subsequently, an embodiment according to the Figures 2a and 2b where the guides remain fixed.

The figures 5a and 5b presents an exemplary embodiment according to this embodiment, the figure 5a representing the fixed inner cylinder 26, stator, equipped with two waveguides 24, 25 and the figure 5b representing the outer cylinder 21, equipped with the helical slot, rotating around the fixed cylinder.
The outer cylinder 21 is rotated by a motor 19, shown in FIG. figure 1 . It slides in rotation relative to the fixed portion via a cylindrical ball bearing device 30. The fixed portion 27 of the ball bearing is mechanically secured to the base of the inner cylinder 26 and the movable portion 27 'of the ball bearing is secured to mechanically of a support 28, for example of cylindrical shape, this support being itself mechanically secured to the outer cylinder 21. The cylindrical support 28 forms for example an enlarged cylindrical base of the fixed cylinder 21, the assembly forming the stator.
The stator and rotor assembly is covered with a radome protection not shown.

The Figures 6a and 6b illustrate a particular embodiment of the guides and their coupling to the outer cylinder 21 advantageously allowing the minimization of microwave leakage as previously mentioned. The figure 6b is a partial sectional view where the radius of curvature has not been shown for reasons of simplification.

• Profondeur d'un guide 24, 25 : 0,75 À ;
• Largeur d'un guide 24, 25 : 0,35 À ;
• Profondeur d'une cavité latérale 52, 53, 53' : 0,25 λ ;
• Largeur d'une cavité latérale 52, 53, 53' : 0,12 λ ;

La distance entre l'ouverture 51 du guide et les ouvertures 54, 55, 54' des cavités d'une part et la face intérieure du cylindre 21 peut aller de 0,1 λ à 2 λ. Dans le cas d'application avec le radar 2 fonctionnant à 77 GHz, λ est de l'ordre de quelques millimètres.The Figures 6a presents, by a partial perspective view, the production of a guide, for example, the transmission guide 24 is considered. The reception guide 25 is produced and coupled in the same way.
The waveguide 24 is a rectangular section guide having a radiating aperture 51. The metallized inner face of the outer cylinder 21 forms a short circuit to close the guide. The rotation of the guide 24 inside this cylinder 21 has the effect of creating a radiating source which moves along its longitudinal opening 22. The waveguide 24 is connected at one end to the radar transmission circuits. 2 and other circuits by transmission means which will be described later. It is connected at its other end to a suitable load.
Two parallel cavities 52, 53 are formed on each side of the guide 24, over its entire length. These cavities being parallel to the waveguide 24, they also follow the helical line 23.
The figure 6b presents the two waveguides 24, 25 each surrounded by a cavity. The emission waveguide 24 is surrounded on the left by a cavity 53 and on the right by a cavity 52. The reception waveguide 25 is surrounded to the left of this latter cavity 52, common to both guides. and on the right by a cavity 53 '.
The openings 54, 55, 54 'of the cavities are substantially in the plane of the opening 51 of the guide, more precisely in the same line of curvature.
Advantageously, these cavities trap the microwave waves and very strongly limit or even eliminate microwave leakage.
These cavities 52, 53, 53 'are less wide and shallower than the guide. The dimensions are for example the following, where λ is the emitted wavelength, corresponding to the central frequency:

• Depth of a guide 24, 25: 0.75 Å;
• Width of a guide 24, 25: 0.35 Å;
• Depth of a lateral cavity 52, 53, 53 ': 0.25 λ;
• Width of a lateral cavity 52, 53, 53 ': 0.12 λ;

The distance between the opening 51 of the guide and the openings 54, 55, 54 'of the cavities on the one hand and the inner face of the cylinder 21 can range from 0.1λ to 2λ. In the case of application with the radar 2 operating at 77 GHz, λ is of the order of a few millimeters.

In the example of Figures 6a and 6b , the guide emits according to the component E, the radiating opening being made on a small side of the guide.
The figure 6b presents a preferred embodiment where the guide 24 and the cavities 52, 53, 53 'are made in the inner cylinder 26. For this purpose, this cylinder may be metallic. As for the waveguides 24, 25, the cavities 52, 53, 53 'can be etched in the cylinder.

The figure 7 specifies, by a partial longitudinal sectional view, an advantageous embodiment where the space 70 between the stator 26 and the rotor 21 is very small, typically having a thickness e typically equal to 0.1 mm with a tolerance of ± 0 , 05 mm.
The height of the scanner 1 is for example of the order of 400 mm.

The Figures 8a and 8b show an embodiment of the device according to the invention for performing both a conventional radar mode of operation, of the single-stat type, and a bi-static mode of operation.
For this purpose, the device comprises two scanners 1, 1 'of the type illustrated by the figures 5a and 5b , the two scanners being connected to the radar 2 according to the figure 8b . The two scanners 1, 1 'are interconnected by two waveguides 83, 84, a guide 83 connecting the transmission guides 24 of the scanners and the other guide 84 connecting the reception guides 25 of the scanners.
The first waveguide 83 is connected via a magic T to the transmission channel 3 connected to the radar. The second waveguide 84 is connected via another magic T to the reception channel 4 connected to the radar.
The set of two scanners and the radar is disposed inside a radome 80, of cylindrical shape. The camera 5 is fixed on this radome between the two scanners 1, 1 '.

The figure 9 illustrates the two modes of operation of the device illustrated by the Figures 8a and 8b . In the single-static mode, a single scanner 1 is used, for transmission to an individual 91 and for reception. In the bi-static mode, the first scanner 1 transmits to the individual and the second scanner 1 'realizes the reception of the signals re-transmitted by the individual.

The bi-static mode of operation advantageously makes it possible to improve the quality of the radar image. The camera 5 is oriented towards the individual in order to capture the video images thereof.

We come back to figure 1 , to describe the formation of the radar images in combination with the stereoscopic camera 5. The radar can operate in single-stat mode or bi-static mode.
The device according to the invention makes it possible to detect and image magnetic or non-magnetic objects hidden under the clothing of a person who is stationary or in motion.
Advantageously, the camera measures the distances on the clothes and, the infrared emission does not penetrate the clothes, allows the formation of a suitable filter in order to obtain a radar imagery of the objects and the determination of their natures, through the clothes .
It should be noted that in the absence of this camera, the radar would not allow the measurement of the different distances of the body parts of moving people, because it would be necessary to operate in FMCW mode (frequency-modulated continuous wave) from 70 GHz to 110 GHz to achieve the desired accuracies which are of the order of a millimeter.

The two waveguides 3, 4 connect the antenna 1 to the radar 2. A first guide 3 transmits the transmission wave to the antenna. This first waveguide 3 also transmits the reception signals from the antenna to the radar. The second guide 4 transmits the reception wave of the antenna to the radar, via a phase shifter performing a phase rotation of 90 ° on the received signals.
Thus, in the direct way, using the first guide 3, the signals are transmitted without phase shift providing the direct component I (t) of the signals received while the second guide 4 provides the quadrature component Q (t).
The components thus received are taken into account by the radar reception and processing means 2 for calculating the radar image obtained, this image being of the SAR type as indicated above.

Où L(x_i ,y_j ,t) est la distance entre la source rayonnante 11, 12 à l'instant t et le point d'analyse (x_i ,y_j ) sur l'individu, λ représentant la longueur d'onde. Les distances L(x_i ,y_j ,t) sont délivrées par la caméra 5. s(t) représente la distance entre le centre de l'antenne émettrice et la caméra.The formation of the image Im ( x _i , y _j ) at a point ( x _i , y _j ) is effected in a known manner by the integration of the signals received in an analysis time T. The image Im ( x _i , y _j ) is then given by the following relation: $$\mathrm{im}\left(x_i,{\mathrm{there}}_j\right)={\displaystyle \underset{0}{\overset{T}{\int }}\left(I\left(t\right)+\mathit{iQ}\left(t\right)\right)}.\exp \left[-\mathrm{<figure-callout\; id="4"\; label="i"\; filenames="imgf0001.png,imgf0008.png"\; state="\{\{state\}\}">i</figure-callout>}\frac{4\pi }{\lambda }\left(\mathrm{The}\left(x_i,{\mathrm{there}}_j,t\right)\right)-s\left(t\right)\right]$$

Where L ( x _i , y _j , t ) is the distance between the radiating source 11, 12 at time t and the point of analysis ( x _i , y _j ) on the individual, where λ is the length of wave. The distances L ( x _i , y _j , t ) are delivered by the camera 5. s (t) represents the distance between the center of the transmitting antenna and the camera.

Advantageously, the camera makes it possible to produce around the target individual a virtual envelope whose distances to the device according to the invention are known. This virtual envelope corresponds in fact to the outer surface of the clothes worn by the individual. It makes it possible to obtain a reference surface. The measurements made by the camera make it possible to obtain a mesh network representing this surface. The surface can be obtained by smoothing by averaging. This surface is calculated at regular time intervals, for example every 20 ms, to focus on each part of the individual in motion (arms, torso, legs ...).
The camera, which may be of the infrared type, having a retina consisting of a network of CMOS sensors measures the distance by the received power level. For a coding carried out on 12 bits for example, the measurement accuracy can be of 1 millimeter at a distance of one meter.

The figure 10 illustrates the detection of an object 103 through a garment 101, the object being fixed on the body 102 of the individual below the garment 101. The distance of the garment, more particularly from its points, is measured and known to the device according to the invention, the garment having been represented as the virtual surface as described above. The obtaining of this envelope is very important because it makes it possible to follow the deformations of the garment due to the body in movement. Indeed, the camera 5 allows distance measurement according to given periods of time, for example every 20 ms, of all moving parts of the body, more specifically of the clothing envelope. These distance measurements allow the formation of a suitable filter for the formation of images.

L'image obtenue est donnée par la relation (1). Pour chaque pixel x, y de l'image on procède au calcul : $${\displaystyle \sum \left(I\left(t\right)+\mathit{iQ}\left(t\right)\right)}.\exp \left[-\mathrm{i}\frac{4\pi }{\lambda }\left(L\left(x_i,y_j,t\right)\right)-s\left(t\right)\right]$$

la partie $\exp \left[-\mathrm{i}\frac{4\pi }{\lambda }\left(L\left(x_i,y_j,t\right)\right)-s\left(t\right)\right]$

correspondant au filtre adapté. (L(x_i ,y_j ,t)) est calculée sur la surface virtuelle formée à partir de plusieurs points mesurés sur les vêtements, sur chaque partie du corps de l'individu en mouvement.
Le bruit causé par les imprécisions de mesures est classiquement filtré par des fenêtres glissantes sur l'image.The imaging process is performed in two steps: an acquisition step and a focusing step. In the acquisition step, the radar acquires the I and Q components of equation (1) above. Since the radar signals pass through the garments, the acquired image is that of the body possibly equipped with an object 103. The determination of the reflection coefficients of the received signals makes it possible to classically define the nature of the parts of the image and in particular of the object 103.
In the focusing step, the camera makes it possible to define the distances forming the argument of the exponential of the integral in equation (1) and thus to calculate the image.
The resolution of the image is equal to $\lambda .\frac{\mathrm{F}}{2\mathrm{D}}.$

The image obtained is given by relation (1). For each pixel x, y of the image, proceed to the calculation: $${\displaystyle \Sigma \left(I\left(t\right)+\mathit{iQ}\left(t\right)\right)}.\exp \left[-\mathrm{<figure-callout\; id="4"\; label="i"\; filenames="imgf0001.png,imgf0008.png"\; state="\{\{state\}\}">i</figure-callout>}\frac{4\pi }{\lambda }\left(\mathrm{The}\left(x_i,{\mathrm{there}}_j,t\right)\right)-s\left(t\right)\right]$$

the part $\exp \left[-\mathrm{<figure-callout\; id="4"\; label="i"\; filenames="imgf0001.png,imgf0008.png"\; state="\{\{state\}\}">i</figure-callout>}\frac{4\pi }{\lambda }\left(\mathrm{The}\left(x_i,{\mathrm{there}}_j,t\right)\right)-s\left(t\right)\right]$

corresponding to the adapted filter. ( L ( x _i , y _j , t )) is calculated on the virtual surface formed from several points measured on the clothes, on each part of the body of the moving individual.
The noise caused by measurement inaccuracies is conventionally filtered by slippery windows in the image.

• Leurs formes ;
• Leurs permittivités diélectriques, révélant leurs natures.

Cette reconnaissance peut être réalisée par le calculateur 6 ou les moyens de traitement du radar.The final image is obtained according to the relation (1) and is calculated by the computer 6 from the image supplied by the radar, the I and Q components, and the image supplied by the camera delivering the argument. the exponential. In a possible embodiment, the computer 6 can be integrated in the radar 2. In particular the function of the computer 6 can be performed by the radar processing means which process the components I and Q of the SAR image.
Once the final image has been obtained, object recognition and classification can be performed by analyzing:

• Their forms;
• Their dielectric permittivities, revealing their natures.

This recognition can be performed by the computer 6 or the radar processing means.

In a particular embodiment, the radar 2 transmits at several frequencies, close to a given frequency, for example 77 GHz. The radar 2 emits for example according to five frequencies F1, F2, F3, F4, F5. In the measurement phase, the pulse is for example divided into five parts, the parts being emitted successively to F1, F2, F3, F4, F5. If the pulse lasts 200 μs, each part then lasts 40 μs.
More generally, the radar transmits continuously (CW), the emission pulse being divided into N parts, each portion corresponding to a frequency. We remain thereafter in the example where N is equal to 5.
In the analysis phase, the phases and amplitudes are for example calculated for all the frequencies. A first analysis at the first frequency F1 is done on the whole body. Then a second analysis is made on a limited area 110 containing a shape detected for the other four frequencies F2, F3, F4, F5, as illustrated by FIG. figure 11 . These different analyzes make it possible to approach the theoretical value of the dielectric permittivity of the object and its thickness.

By way of example, measured values of 2.9 and 11 mm respectively of the dielectric permittivity and the thickness for theoretical values of 3.1 and 10 mm can be achieved.

The figure 12 shows an exemplary embodiment of a device according to the invention, portable. The antenna part consisting of one or two scanners 1, 1 ', the radar 2 and their interconnection means 3, 4, 83, 84 are arranged inside a cylindrical structure which also acts as a radome 80. structure also supports the camera 5. The structure 80 is connected to a handle 120 for obtaining a portable device, easily manageable and lightweight. Its realization cost may be low because of the type of components used, especially the radar 2 can be a car-type radar, economic, and the camera may be Kinect type, also economic. The components constituting the scanner interior (cylinders, waveguides, motor and ball bearings) are also economical.
This provides a device for detecting illicit objects by detecting forms through clothing and characterizing their material. It can be used in motion. The detection can easily be done by pointing the device to about one meter from an individual to control.
The detection device is connected to viewing means by a suitable wireless link. The visualization means 7 may be a screen disposed in a control center or be within the reach of the user who manipulates the device. The display means may also be glasses worn by the user and on which the detected images are projected.
It is possible to provide a second stereoscopic camera to improve the field of view.

The figure 13 presents another example of use of a device according to the invention with another "packaging". The control system is here applied at doors 131, 132 opening automatically. Four devices according to the invention, two of which are represented by their radomes 80, can be used. For each door, a device is placed to the outside and a device is placed inward, each device being placed closer to the opening. As in the example of the previous figure, an individual or a moving object can be controlled from all angles. A display screen, common to all four devices, is placed at a distance.

The examples of previous achievements show that the invention improves the fluidity of controls, especially in places of passage, such as for example airports, railway stations or shopping centers or other public places.

Claims (11)

1. Device for detecting objects borne by immobile or moving individuals, characterized in that it includes at least:

   - at least one rotary antenna (1, 1') including at least two parallel rectilinear waveguides (24, 25) and a cylinder (21) provided with a helicoidal slot (22) rotatably movable about said guides, which guides are open facing the interior face of said movable cylinder, said surface forming a microwave short-circuit in order to close said guides, one of said guides (24) being dedicated to emission, a movable radiating source (11, 12) being located facing said guides subsequent to the rotational movement of said cylinder (21) inducing a movable emission and reception beam able to be oriented towards an individual;

   - one radar (2) emitting a continuous wave (CW) microwave signal towards the emission guide (24) of said antenna and receiving the signals received from the guides (24, 25) of said antenna, which signals are captured by said movable beam, said received signals being the direct component I and the quadrature component;

   - one stereoscopic video camera (5) that is oriented in the same direction as said movable beam and able to record the clothing envelope of said individual, said envelope serving as a reference surface for the measurement of distances to said device;

   - one processor (6) that computes an SAR image of that portion of the body of said individual which is targeted by said radar and said video camera and who is possibly equipped with one or more objects (103), from signals received from said radar (2) and the distances measured by said video camera (5).
2. Device according to Claim 1, characterized in that the two guides (24, 25) being etched into a cylinder (26) placed in the interior of the movable cylinder (21), the two cylinders having the same axis (100), the space between the two cylinders is equal to 0.1 mm ± 0.05 mm.
3. Device according to either one of the preceding claims, characterized in that said rotary antenna (1, 1') includes a system for minimizing microwave leaks, said system being composed of three cavities (52, 53, 53'), said cavities being arranged pairwise on each side of said waveguides (24, 25), parallelly thereto, over all their length.
4. Device according to any one of the preceding claims, characterized in that said waveguides (24, 25) being etched into a cylinder (26) placed in the interior of the movable cylinder (21), said movable cylinder (21) and said interior cylinder (26) are rotatably movable by way of a ball bearing device (30), the base of said movable cylinder (21) and the base of said interior cylinder (26) being mechanically secured to the movable portion (27') and the stationary portion (27) of said device (30), respectively.
5. Device according to any one of the preceding claims, characterized in that said radar (2) operates in a millimetre-wave frequency band.
6. Device according to any one of the preceding claims, characterized in that it includes two rotary antennae (1, 1') so that said radar may operate in a bi-static mode, one antenna (1) realising the emission and the other antenna (1') being dedicated to the reception.
7. Device according to Claim 6, characterized in that the antennae (1, 1') are connected together by two waveguides (83, 84), one guide (83) connecting the emission guides (24) of said antennae and the other guide (84) connecting the reception guides (25), the first waveguide (83) being connected via a magic T to a waveguide (3) that is connected to the radar and the second waveguide (84) being connected via another magic T to a waveguide (4) that is connected to the radar.
8. Device according to any one of the preceding claims, characterized in that said radar (2) emits at a number N of frequencies close to a given frequency, the emission pulse being divided into N portions, each portion corresponding to one frequency, a first level of analysis of the image being performed for the signals received at the first of said frequencies (F1), other analyses being performed for the signals received at the other frequencies (F2, F3, F4, F5), the various analyses allowing the theoretical value of the dielectric permittivity of a detected object to be approached.
9. Device according to any one of the preceding claims, characterized in that the processor (6) is an integral part of the processing means of said radar (2).
10. Device according to any one of the preceding claims, characterized in that it includes means (7) for viewing the obtained images, said viewing means being glasses worn by a user and onto which said images are projected.
11. Device according to any one of the preceding claims, characterized in that the antennal portion (1, 1'), the radar (2) and their interconnecting means (3, 4, 83, 84) are placed in the interior of a portable cylindrical structure (80) that also plays the role of a radome, said structure supporting said video camera (5).

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